Paper machine dryer condensate control



July 7, 1959 E,J JUSTUS ET AL 2,893,136

PAPER MACHINE DRYER CONDENSATECONTROL Filed July 5, 1957 .UWM/' l Edgarrf. r/ufu Raber A. aaz

United States Patenti() PAPER MACHINE DRYER coNnENsATE CONTROL dgar J.`ustus and Robert A. Daane, Beloit, Wis., assignors to Beloit IronWorks, Beloit, Wis., a corporation of Wisconsin Y Application July 5,1957, Serial No. 670,144 6 Claims. (Cl. 34-119) The instant invention'relates to a dryerl drum for a paper machine, and more particularly, toan improved 'dryer drum structure. As conventionally employed in theart, dryer drums for paper machine drying sections generally consist ofa cylindrical shell, spacedv heads extending radially across the shellto close the open ends thereof and carrying means for journaling theshell for rotation, and means for introducing steam into the interior ofthe shell and drawing condensate therefrom. The Yankee dryer drum hasgenerally the same structural arrangement as now used in the art, exceptthat the Yankee dryer drum isordinarily of substantially greater vsizethan the dryer drums in the conventional dryer section of a papermachine. Nevertheless, in each case these dryer drums (whether the largeYankee dryer drum pr' the smaller conventional drum) has certainoperating limitations. i

In the prior art paper machine dryers, steam is admitted `tothe interiorof the dryer and is in contact with the entire interior surface of thedryer, the inner cylinder wall being subject, therefore, to uniformtemperature. Condensate forms on the inner surface of the cylinder andthe condensate layer depth is substantially uniform 4at the minimumthickness or depth obtainable with siphon equipment used. The outer wallof the dryer, however, is subject to variations in temperature. Forexample, the moist paper web may not extend the full length of thecylinder shell, so as to leave the ends thereof uncovered by the paper.Also, the paper web passing over the cylindrical shell may not be dried,to the same eX- `tent in the central portion as it is at the edgesthereof.

In addition, the rate of drying or rate of water evaporation from theweb may vary across the width thereof, because of prior irregularitiesin the processing of the web, or different characteristics in the web,or different draft conditions in the dryer. In particular, however, thedryer surface in the region of the heads is not cooled by the passingdamp sheet and it is subjected to cooling only from the ambient airwhich, of course, may vary greatly in relative humidity and/ ortemperature. In general, the cooling effect at the end reaches of theshell is less than that in the intermediate portion.

vvThe instant invention provides a simple and economical means forovercoming this diiiiculty. It will be appreciated that the tendency forthe ends of the shell to become overheated, or more greatly heated thanthe intermediate portion, results in a tendency to overdry the edges ofthe web adjacent thereto, as well as an u-nnecessary heat loss. In theinstant invention, however, means are provided for maintaining a layerofv predetei-mined depth of condensate against the inner periphery ofthe end portions of the shell to reduce heat transfer from the steam tothe shell body in these regions. It will be appreciated that the instantinvention may be employed to reduce heat transfer from the steam to anyparticular portion of the shell desired, although the main problem heresolved is that of reducing heat losses at the shell ends and reducingoverheating of the shell ends.

ice

The prior workers in the art have proposed countless devices forminimizing the depth of condensate layer con tinuously forming on theinner shell surface. In contrast, the instant invention resides in theuse of means for maintaining a greater condensate layer in apredetermined portion of the shell (for example, at the ends thereof)for the purpose of reducing heat transfer and heat loss at this regionof the shell. In addition, the instant invention provides means forcontrolling the depth of condensate in such regions, so as to controlthe rate of heat transfer to the shell by, in effect, placing aninsulator layer (of condensate) between the live steam and the cylindershell.

It will be appreciated that the dryer drums operate at speeds sufhcientto cause the condensate to be retained in substantially uniform deptharound the entire inner periphery of the shell because of centrifugalforce. Accordingly, the instant means yemployed to maintain a differentcondensate depth at selected axial portions of the shell are in the formof axially spaced circumferential dams, or a single circumferential damaxially spaced from one of the shell heads to maintain 4a predeterminedlevel of condensate between such dam and the shell head.

It is, therefore, an important object of the instant invention toprovide an improved dryer drum structure.

Another object 0f the instant invention is to provide an improved dryerdrum having 'means therein to retain a layer of condensate that iscontrollable in radial thickness, in order to regulate heat transferrate from the heating fluid in the dryer drum to the outer periphery ofthe dryer.

A further object of the instant invention is to provide a dryer drumhaving means to position a retained layer of condensate therein to suitthe heating requirements of a web trained over the dryer drum.

Other and further objects, features and advantages of the presentinvention will become apparent to those skilled in the art from thefollowing detailed disclosure thereof and the drawings attached heretoand made a part hereof.

On the drawings:

Figure 1 is a partial sectional elevational view of a dryer drumembodying the instant invention;

Figure 2 is an enlarged detail view of another em bodiment of theinstant invention, shown in a fragmentary sectional elevational view;

Figure 3 is a fragmentary detail elevational sectional view takensubstantially along the line III-III of Figure 2;

Figure 4 is a fragmentary plan view of a connected portion of acircumferential dam used in the practice of the instant invention; and

Figure 5 is an elevational view of the connected portion shown in Figure4.

As shown on the drawings:

The reference numeral 10 indicates generally a dryer drum of the presentinvention, only' the lower half of which is shown in Figure 1 insectional elevation for simplification of the description of the instant,invention. The dryer drum 10 includes a cylindrical Vshell 11 havingopen ends closed by annular heads 12 and 12a, secured to the ends of theshell 11 bybolts 13 and4 extending radially across the ends of the shell11. Journals 14, 14a are integrally formed with the heads 12, 12a,respectively, and. extend axially outwardly therefrom to be received bysuitable bearings (not shown) for rotatably mounting the drum 10. Eachof the journals 14, 14a is provided with an axial bore 15, 15a. Theaxial bore 15a at one end is sealed oif by a plate 16a in the particularstructure here shown, whereas the opposite axial bore 1S mounts a plate16 which receives a steam inlet header 17 connected to a suitable sourceof steam S (as shown diagrammatically). The steam ows from the source Sthrough the steam inlet line 17 which leads into the shell 11 throughthe head 12, and the steam enters the interior of the shell 11 throughan apertured head 18.

The steam within the shell 11 is continuously condensed and thecondensate deposits as a iilm on the inner periphery of the shell 11.The condensate thus formed collects along the inner periphery of theshell 11 and is maintained thereagainst in a substantially uniformthickness of liquid by virtue of centrifugal force resulting from therotation of the dryer drum 10. A Siphon nozzle 19 placed against thecentral inner periphery of the shell 11 picks up condensate and returnsthe same through a radially aligned pipe 20 to a central condensateheader 21 which is concentrically mounted within the steam inlet header17 and passes out through the shell head 12 into suitable receivingmeans such as a drain D (shown diagrammatically) The foregoingdisclosure relating to the dryer drum 10 describes a typical prior artstructure. It will be appreciated that the steam inlet line may leadthrough one head and the condensate line through the opposite head.Other variations in the arrangement of the elements consistent with theknowledge of the prior art are of course permitted. The instantinvention provides a means for controlling the heat transfer through theshell 11 at various points. As indicated in Figure 1 a web W is trainedabout the outer periphery of the shell 11, but this web W leaves exposedend portions 11a and 11b of the shell 11, which are cooled only byambient atmosphere. The web edges Wa and Wb may also be dryer than themain body of the web W, or may be inclined to dry more rapidly, ifsubjected to the same amount of heat.

As will be seen from Figure l, a circumferential dam 22 is mounted onthe inner periphery of the shell 11 at the shell end 11a adjacent thehead 12a. The circumferential dam 22 is aligned approximately with theextreme edge of the web W, so that the end portion of the shell 11between the head 12a and the dam 22 is the end portion 11a of the shell11 which is not covered by the web W. The circumferential dam 22cooperating with the head 12a maintains a level L of condensate againstthe inner periphery of the shell 11. This level L is substantially thesame throughout the periphery in this end portion 11a of the shellbecause of centrifugal force. The level L of condensate, however,functions as an insulator reducing the rate of heat transfer from thelive steam within the shell 11 to the outer shell periphery in theregion 11a. In this way heat losses to the ambient atmosphere arereduced readily, simply and economically. At the opposite end of theshell 11 there is mounted a circumferential dam 23 which cooperates withthe head 12 to maintain a level L of condensate therebetween on theinner periphery of the shell end 11b which functions in the same manneras the level L of condensate at the opposite end of the drum 10.

If the drum 10 is to be operated at speeds below which rimming of thecondensate occurs in the channel between the dams and end heads, paddlesor batlles (not shown) can be mounted in the channels to reduce rotationof the condensate with the drum. Thus in slow speed paper machineproducing heavy weight sheets or boards excess condensate builds upbetween the dams 22 and 23,

the centrifugal force developed in a slow rotating drum Y may not besuflicient to insure movement of the condensate with the drum to rim theliquid around the inner periphery of the drum. Transfer paddles or balesspaced circumferentially across the channels will drive the liquid withthe drum It will be noted that these circumferential dams 22 and 23 areaxially spaced annular members on (and integral with) the innerperiphery of the shell 11 spaced a short distance from the heads 12 and12a. The circumferential dams 22 and 23 extend inwardly a shortpredetermined distance, so that condensate may ow over such dams towardthe central portion of the shell 11, if

and the heads 12, 12a. The dams 22 and 23 thus project inwardly a shortdistance to retain condensate at each end of the shell 11 Whilepermitting ow of excess condensate thereby toward the intermediateregion or central portion 11a` of the shell 11. It is apparent that theSiphon 19 functions in the intermediate portion 11c of the shell 11,since it is important to keep the condensate film at a minimum thicknessin this region in order to obtain best heat transfer conditions.

It will also be noted from Figure l that an additional annular ridge 24is mounted in closely spaced relation to the ridge 22, so as to align aspace therebetween with the edge portion Wa ofthe web W. The ridge 24functions similarly to the ridge 22, except that the ridge 24 does notextend inwardly as far and the level l of condensate retained therebyopposite the web edge Wa is less than the level L of condensatemaintained adjacent the head 12a. In this way more heat is transmittedfrom the live steam within the shell through the shell 11 and to the webedge Wa than is transferred through the shell end portion 11a, but lessheat is transferred to the web edge Wa than is transferred to the mainbody of the web W through the central or intermediate shell portion 11e.A circumferential dam 25 at the other end of the shell functions in theway the dam 24 functions to maintain a level l' of condensate betweenthe dams 23 and 25 that is lower than the level L between the head 12and the dam 23.

As will be appreciated, the means for maintaining the level ofcondensate against the shell wall need not be in the form of a dam (suchas the dams 22, 23, 24 and 25) wherein the control means is provided inthe form of the top of the dam over which the condensate ilows. Instead,as shown in Figure 2, a circumferential dam 26 may be provided with anaperture 27 therein for maintaining a condensate level L-l. In Figure 2parts corresponding to the parts in Figure l are indicated with the samereference numeral in the series, so itis apparent that Figure 2 shows ashell 111 with an uncovered shell end 111a and a head 11211 securedthereto by bolts 113. The circumferential dam 26 of Figure 2 extendsaround the entire inner periphery of the shell 11 and is provided with aplurality of apertures 2.7 through which condensate may ow toward thecentral portion of the shell 11, but which serve to control thecondensate level L-1.

As shown in Figure 3, a plurality of apertures at levels 27, 28 and 29are provided in the annular ridge 26 for maintaining levels L-1, L-2,L-3, respectively. Only the apertures 27 are open in Figure 3 (with theapertures 28 and 29 plugged), so that the level L-1 is maintained, butwhen it is desired to operate at a different condensate level, the holes28 or the holes 29 may be unplugged.

As shown in Figures 4 and 5, if the circumferential dam or annular ridgeis not integral such as the ridge 22 and is a separate element such asthe ridge 26, then it may be mounted within the shell 111 by a number ofways. As shown in Figures 4 and 5, the annular member 26 may be split atone end 26a to receive a boss portion 26h at the opposite end 26C, witha stop 26d mounted on the boss portion 26h. Adjustable means in the formof a set screw 26e is carried by the split end 26a and acts against thestop 26d so as to urge the annular ridge 26 into tight contact with theinner periphery of the shell 111. Other means may, of course, beemployed for mounting the ridge 26 so as to permit subsequent changes inposition thereof.

It will also be appreciated that the instant invention affords a uniqueadvantage with respect to the control of heat input to the webthroughout an entire dryer section, which may include as many as 50dryer drums.

. In such an arrangement the dams within the dryer drums are positionedat different locations throughout the dryer section, so thatthe amountof heat input to the central portion of the web may be correlated withthat to the web edges (Wa and Wb). In other words, these dams may bepositioned so as to produce a contoured curve of total heat input to theweb. For example, in a paper machine having a dryer section of 50dryers, the dams can be successively moved toward the center of themachine in such a manner that the edges of the web Would receive a heatinput of 60% of the input at the center of the machine or dryer, and byproper arrangement, the total heat input at intermediate points isprecisely adjusted to the desired moisture prole, and/ or to theparticular characteristics of drying due to ventilation and otherfactors.

In such a paper machine dryer section, the circumferential dams withinthe dryer drums are moved progressively inward toward the center of thedrums (in the direction of web travel) from the oncoming to theoffrunning side of the dryer section, and with such dams mounted in thedrums in this manner a substantially uniform ratio between the heatinput to the central portion of the web and that to the edges may bemaintained throughout the length of the dryer section.

It will be understood that modifications and variations may be effectedwithout departing from the spirit and scope of the novel concepts of thepresent invention.

We claim as our invention:

1. A dryer drum comprising a cylindrical shell, a head closing each endof the shell, a steam inlet line leading into the shell through one ofsaid heads, axially spaced annular members on the inner periphery of theshell spaced from said heads for restricting ow of condensate from theregions of said shell adjacent the heads to the intermediate region ofthe shell, and a condensate drainage line communicating with the innersurface of the shell only between said members and leading from theintermediate region of the shell through one of said heads receivingsteam and condensate from the shell.

2. A dryer drum comprising a cylindrical shell, a head closing each endof the shell, a steam inlet line leading into the shell through one ofsaid heads, annular ridg on the inner periphery of the shell near butspaced from the heads at each end of the shell projecting inwardly ashort distance to retain condensate at each end of the shell whilepermitting ow of excess condensate thereby toward an intermediate regionof the shell, and a condensate drainage line communicating with theinner surface of the shell only between said ridges and leading from theintermediate region of the shell through one of said heads receivingsteam and condensate from the shell.

3. A dryer drum comprising a cylindrical shell, a head closing each endof the shell, a steam inlet line leading into the shell through one ofsaid heads, annular ridges on the inner periphery of the shell near butspaced from the heads at each end of the shell projecting inwardly ashort distance to retain condensate at each end of the shell, saidridges having apertures therein controlling the level of condensate atthe shell ends while permitting flow of excess condensate thereby towardan intermediate region of the shell, and a condensate drainage linecommunicating with the inner surface of the shell only between saidridges and leading from the intermediate region of the shell through oneof said heads receiving steam and condensate from the shell.

4. A dryer drum comprising a cylindrical shell, a head closing each endof the shell, a steam inlet line leading into the shell through one ofsaid heads, annular ridges on the inner periphery of the shell near butspaced from the heads at each end of the shell provided with condensatelevel control means for maintaining a level of condensate in the spacebetween each ridge and the head adjacent thereto while permitting ow ofexcess condensate thereby toward an intermediate region of the shell,and a condensate drainage line communicating with the inner surface ofthe shell only between said ridges and leading from the intermediateregion of the shell through one of said heads receiving steam andcondensate from the shell.

5. A dryer drum comprising a cylindrical shell, a head closing each endof the shell, a steam inlet line leading into the shell through one ofsaid heads, a pair of closely spaced annular ridges on the innerperiphery of the shell near but spaced from each head in the shell, saidridges being provided with condensate level control means formaintaining a level of condensate in the space between each pair ofridges and in the space between each head and the nearest ridge theretowhile permitting flow of excess condensate thereby toward anintermediate region of the shell, and a condensate drainage linecommunicating with the inner surface of said shell only between saidridges and leading from the intermediate region of the shell through oneof said heads receiving steam and condensate from the shell.

6. A paper machine dryer section containing a plurality of dryer drumssuccessively contacting a web traveling therethrough from the oncomingto the off-running end of the dryer section, each of said dryer drumscomprising a cylindrical shell for engaging the web, a head closing eachend of the shell, a steam inlet line leading into the shell through oneof said heads, circumferential dams on the inner periphery of the shellnear each end thereof maintaining a level of condensate on the sidethereof adjacent the shell end, and a condensate line communicating withthe inner surface of the shell on the other side only of said dams andleading therefrom through one of said heads; the dams in each of saidshells being placed successively closer to the middle of the shell fromthe oncoming to the off-running end of the dryer section so as toeffectively maintain a desired ratio of heat input to the central webportion with respect to heat input to the web edge portions.

References Cited in the le of this patent UNITED STATES PATENTS2,677,898 Ohlson et al. May l1, 1954 FOREIGN PATENTS 2,284 Great Britain1878 18,155 Great Britain 1913 160,380 Great Britain Mar. 24, 1921547,191 Germany Mar. 23, 1932

